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2013FallShotcreteEMag

Nozzleman Knowledge Dry-mix equipment maintenance By Todd Ferguson m get the most efficient production, max- loosened material with a screwdriver.Over time, the wear plate will become misshapenbowl right-side-up again and carefully remove theaintaining your dry-mix shotcrete (gunite)equipment ensures that your crew will imum service life, and safest operation from your from constant contact with dry shotcrete material. machinery and accessories. The typical dry-mix Grooves may appear in the walls of the pockets or shotcrete equipment setup includes a gunite the surface of the plate may become uneven (that is, machine, material nozzle, material hose, water not completely flat). When this occurs, the wear plate hose, air compressor, and air hose. Equipment will not function correctly, causing air leaks between manuals from manufacturers should detail all the the bowl and the plate or uneven rotation. The wear necessary steps for complete equipment mainte- plate should then be resurfaced by “Blanchard” nance. Still, it is important to review these pro- grinding or comparable technology described in the cedures with members of the crew, especially equipment manual (Fig. 2). those in charge of the equipment on a daily basis. The wear pad functions as a seal between the wear plate and the gooseneck outlet assembly and Dry-mix Shotcrete (Gunite) is in direct contact with the flow of material. Over time, the wear pad will develop grooves from machines: Bowl type material passing over it and should be replaced. Gunite machine maintenance begins on the Grooves in the wear pad can allow excess material first day you put it into service. When setting up to cause additional wear on the plate. Manufac- equipment for initial use, you will complete pre- turers highly recommend replacing the wear pad ventative maintenance procedures, such as lubri- as soon as grooves appear. Replacement at regular cation. Two main classes of gunite machines are intervals will prolong the life of the wear plate, in use today: bowl-type gunite machines and ensure the efficient flow of air in the system, and barrel-style gunite machines. Both are considered reduce escaping dust at the gooseneck assembly “rotary” gunite machines (rotary guns), as they (Fig. 3). An overabundance of dust-creating mate- both are designed with rotating feed systems. rials on the job can lead to unsafe working condi- These designs are in contrast to pressurized tions. Contractors should be sure to limit the single- and double-chamber guns, which have exposure of their crew to potentially harmful fallen out of popular use. This article will focus components that may be present in dry-mix mate- on bowl-type designs (Fig. 1). rials. If you find a mound of dry-mix material next Bowl-type gunite machines contain a feed to your gunite machine, there is something wrong system including a material feed bowl, steel wear and the equipment should be checked. The wear plate, rubber wear pad, and material outlet, also pad is the first item to check for wear when mate- known as the “gooseneck.” Owners will have to rial is escaping. Never try to extend the life of a replace the wear plate, wear pad, and a polyure- wear pad with excessive tightening of the hold- thane liner within the gooseneck at various inter- down clamps. This can cause undue stress on other vals of service. Clean the entire bowl and oil its components on the machine and could potentially pockets each day to prevent accumulation. Feed lead to unsafe operation (Fig. 4). bowls are either designed with steel or a combina- A strip of felt provides a seal where the bottom tion of steel/polyurethane. To remove buildup on of the hopper meets the wear plate. This felt seal a steel feed bowl, use a hammer and chisel. To should be lubricated daily until it is flexible remove buildup on a steel/poly bowl, turn it enough to provide an adequate seal. Once the felt upside down and strike it with a rubber mallet seal is dry and hardened, you will need to replace first to loosen any buildup material. Then turn the it. Some manufacturers have provided a conve- 38 Shotcrete • Fall 2013


2013FallShotcreteEMag
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